Bi-metallic circuit breaker snap reed



Aug. 4, 1964 IHI.EGEV 3,

BI-METALLIC CIRCUIT BREAKER SNAP REED Filed April 7, 1961 INVENTOR Haws 56E ATTORNEYS United States Patent 3,143,614 BI-METALLIC CIRCUIT BREAKER SNAP REED Hans Ege, Chicago, Ill., assignor to Underwriters Safety Device Company, Chicago, 111., a corporation of Illinois Filed Apr. 7, 1961, Ser. No. 101,460 4 Claims. (Cl. 200-113) The invention relates to a new and improved form of bi-metallic reed for use in a circuit breaker device. More specifically, the invention is directed to a new and improved bi-metallic reed which is of unique design and configuration and which is particularly adapted for use in circuits of low amperage with positive, fast, fiutterless snap action.

Circuit breaker devices including a bi-metallic reed as a part thereof are subject to many uses under, widely variable conditions. By way of example, reed-type circuit breakers are used in battery chargers to protect against overheating of the battery being charged, in trucks and other vehicles to protect against shorts in the various electrical circuits, and in hot air hand driers, etc. The reeds are formed from diverse metals which are lamina-ted together under pressure. Such metals include brass and steel with the brass acting faster than the steel in response to heat developed as a result of current flowing through the reed. The response to heat build-up in the reed is controlled by the particular configuration or design of the reed which is often based on the controlled provision of sized areas through which the current flows. The reed is tensioned in some respects, usually by dishing and/or dimpling, to provide the same with a reversible concave-convex shape. Thus with the widely variable use of circuit breaker bi-metallic reeds, it is often the case that for given circuit operating conditions the reed used must be specially designed in order to function properly in the specific environment.

It is an object of the present invention to provide a new and improved bi-metallic reed for use in a circuit breaker-device, the reed being of special design and configuration particularly adapting the same for response to low amperages.

A further object is to provide a new and improved bimetallic reed for use in a circuit breaker device, the reed being of unique design and configuration particularly adapting the same for efficient response to low amperages, and further 'being of generally uncomplicated structure permitting economical manufacture thereof.

Other objects not specifically set forth will become apparent from the following detailed description of the invention made in conjunction with the accompanying drawing wherein:

' FIG. 1 is a fragmentary perspective of a circuit breaker device having the new and improved reed of the present invention operatively mounted thereon;

FIG. 2 is a longitudinal section of the device of FIG. 1 on reduced scale taken generally along line 2 -2 therein and illustrating the reed in side elevation;

FIG. 3 is a transverse section of the device of FIG. 1 taken generally along line 3-3 therein; and

: FIG; 4 is a' partly sectioned plan along line 4 4 in FIG. 2. I The drawing illustrates aconventional type of circuit breaker device which, as best shown in FIGS. 2 and 3, comprises mounting block provided with a removable cover member 11. The block 10 has received therethrough a pair of vertically directed terminal studs 12 and 13 which include a reed mounting terminal head 14 and a contact head 15 both of which project upwardly from the top surface of the base 10. The outer depending ends of the studs 12 and 13 are suitably threaded for receiving view taken generally 3,143,614 Patented Aug. 4, 1964 wire leads thereon clamped between nuts 16 and other suitable fastening means not shown.

The new and improved bi-metallic reed 17 of the present invention is operatively mounted above the base 10 in the interior of the cover member 11. The reed as best shown in FIGS. 1 and 4 is of generally rectangular'out line and is sub-divided along its major axis into an endmost mounting portion 18, a central snap action portion 19, and an opposite endmos-t contact portion 20. The reed 17 is formed from any suitable laminated metallic materials which exhibit sufficiently different thermo-responsive properties and which are highly current conductive in order to basically respond and function in the manner which is expected with regard to known types of circuit breaker reeds. The mounting portion 18 is provided with a centrally located aperture by means of which the reed is fixedly secured to the terminal head of the stud 12. The contact portion 20 is provided with a disc-like contact member 21 on the undersurface or bottom face thereof and located for flat engagement with the top surface of the contact head 15 of the terminal stud 13 when the reed is in its closed circuit position. The contact disc 21 may be formed from silver or the like and suitably welded to the contact portion 20 of the reed.

' The central snap action portion 19 of the reed 17 is of special design and configuration to impart new and improved operational aspects to the basic reversible snap action functioning of reeds in general. This portion is provided with a generally H-shaped aperture consisting of paralleling end slot portions 22 and 23 which are centrally interconnected by a longitudinally extending 'slot portion 24. The slots 22 and 23 terminate well inwardly from adjacent side margins of the reed 17 thus providing neck-like current conductive areas longitudinally of the reed. The connecting slot portion 24 has its major axis coinciding with the longitudinal major axis of the reed 17 and may be of slightly greater width than the effec tive widths of the slot portions 22 and 23.

The centrally located H-shaped aperture of the reed 17 actually defines a pair of inwardly and opposite directed, juxtaposed snap action panel portions 25 and 26. These panel portions are each integrally formed with the reed inwardly of the side margins thereof along a theoretical line or area extending between adjacent ends of the transverse slot portions 22 and 23. Thus the panel portions 25 and 26 are free from one another and from the reed centrally thereof for independent action in the manner to be described. The reed 17 is further provided with a pair of transversely aligned circular apertures 27 located on opposite sides of the connecting slot portions 24 of the H-shaped aperture and between the paralleling transverse slot portioi1s-22 and 23 defined thereby. In other words, each panel portion 25 and 26 is provided with a centrally located circular aperture which is confined within the free margins'of the panel portion and the adjacent side margin of the reed. The generally central location of the circular apertures 27 in each panel portion provides for acontinuous circumferential neck-like area for current conductive purposes. This aspect is best illustrated in FIG. 4 wherein current flow is illustrated by broken lines. It should be'particularly noted that current flows about each circular aperture 27 in a direction from the mounting terminal 14 to the contact terminal 15.

As best shown in FIGS. 2 and 3, the reed 17 is preformed with a dished shape which in conjunction with the specific design defined above permits reversible snap action operation of the reed. The broken lines in FIG. 2 illustrate the reversed dishing of the reed 17 when the operating portions thereof reach a predetermined temperature thus resulting in a breaking or opening of the circuit in which the device is connected. The reed as initially formed is completely flat and the various apertures defined above are readily formed therein by use of an inexpensive die stamping operation. The dishing of the overall configuration of the reed is accomplished by the provision of dimple-like indentations 28 in the necklike areas extending between the circular apertures 27 and the adjacent side margins of the reeds. The dimples 28 formed may be of any suitable configuration as the basic purpose is to stretch this neck-like areaout of the plane of the reed to tension the central snap action portion 19 and provide the over-all concave-convex shape to the reed. As illustrated, a'single dimple-like material tensioning portion 28 is 'used along each side margin of the reed and each dimple extends fully across its respective necklike area in alignment with the center of the adjacent circular aperture 27., Preferably, the side marginal necklike areas in which the dimples 28 are formed constitute the narrowest neck-like areas of the reed to provide for highest temperature build-up therein during use of the reed.

The reed design described provides for sensitive positive snap action without fluttering. The reed is particularly adapted'for use in circuits handling low amperage such as on the order of 5 and '6 amps. In this respect, it has been found that the reed 17 has particular utility in a range from about 4 to 20 amps. A

The actual functioning of the various portions of the reed described above is best illustrated in FIG. 1. The solid line positioning of the reed 17 illustrates the same in the closed circuit condition in which the'bottom surface of the reed is concave and the top surface of the reed is convex. Because of the location of the dimples 28 in conjunction with the other structural features of the reed, the entire reed itself is of concave-convex configuration throughout. Upon adequate temperature buildup, particularly in the neck-like areas including the dimples 28, the reed will reverse its shape to an extent that the. top surface thereof becomes generally concave and the bottom surface thereof becomes generally convex. With this action the contact 21 separates from the contact terminal 15 and the associated circuit is open. The reed takes the configuration generally illustrated-in broken lines in FIG. 1. With regard to this configuration, it should be particularly noted that the panel portions 25 and 26 actually become downwardly inclined relative to their initial'slightly bowed condition in the circuit closing configuration of the reed. Thus the panel portions 25 and 26 actually move out of the initial plane of the reed in its'circuit opening configuration and toward the inner free edges thereof project downwardly from the reed. This feature constitutes animpontant asp'ectj'of the invention and is not due solely to the provision of the H-shaped' aperture but is due to'the overall combination of structural features described. t

For use with lower amperage circuits, the reed design preferable involves the location of the circular apertures 27 in closer proximity to'the transverse slot portion 23 than to the transverse slot portion 22. As previously mentioned, the circular apertures 27 are positioned sufficiently away from the innerfree margins of thepanel portions 25 and'26 to define the neck-like areas in which the dimples 28are'f'ormed as being of lesser width'than any of the other neck-portion areas. Positioning of the circular apertures 27 back further on'th'e reed toward the transverse slot portion 22 and away from thetransverse slot portion 23 will provide for efiicient utilization of the reed in circuits handling higher amperages. Thus with the particular combination of design features described, a series of reeds each best usable with specified amperages may be provided while still relying on the basic design features. In other Words, by judicious variable positioning of the circular apertures 27 and bridging dimples 28 along a line of centers between the transverse slot portions 22 and 23 will supply reeds which may be used effectively with a variety of circuits designed for handling different amperages. V V

Obviously certain modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitationszshould be imposed as are indicated in the appended claims.

I claim: a j 1. A bi-metallic reed for use in a circuit breaker device, said reed being'of generally rectangular outline and sub-divided along its major axis into an endmost mounting portion, a central snap action portion, and an opposite endmost contact portion, thesub-division of said reed being provided primarily by a generally H-shaped aperture located centrally thereof and confined well within the side and end margins of said reed, said H-shaped aperture having the paralleling slot portions thereof extendingtransversely of said reed and paralleling the end margins thereof, the connecting slot portion of said H- shaped aperture extending longitudinally of said reed along the-major axis thereof, a pair of inwardly and oppositely directed juxtaposed panel portions defined by said H-shaped aperture inwardly of said side margins be tween said paralleling slot portions, a circular aperture confined within each of saidpanel portions and in trans-v verse alignment on opposite sides of the connecting slot portion of said H-shaped aperture-between the paralleling slot portions (thereof, said circular apertures being dimensioned to define electrical conducting neck-like areas between the circular apertures and the side margins of said reed and adjacent portions of said. H-shaped aperture, the neck-like areas between said circular apertures and the side marginsof said reed. being stretched out of the plane of said reed to tension said central snap action portion and provide said reed with a'dished shape.

2. The bi-metallic reedof claim 1. wherein said necklike areas between. said circular apertures and the sidel margins of said reed are each provided with a single dimple which extends fully across each neck-like area in alignment with the center of the adjacent circular aperture.

3. The bi-metallic reed of claim 1 wherein said necklike areas between said circular apertures and the side margins of said reed constitute the narrowest neck-like areas of said reed for highest temperature build-up therein during use of said reed. i Y

4. The'bi-r'netallic reed of claim 1 wherein said circular apertures are in closer proximity to the paralleling slot portion bordering the contact portion of said reed than the remaining paralleling slot portion.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A BI-METALLIC REED FOR USE IN A CIRCUIT BREAKER DEVICE, SAID REED BEING OF GENERALLY RECTANGULAR OUTLINE AND SUB-DIVIDED ALONG ITS MAJOR AXIS INTO AN ENDMOST MOUNTING PORTION, A CENTRAL SNAP ACTION PORTION, AND AN OPPOSITE ENDMOST CONTACT PORTION, THE SUB-DIVISION OF SAID REED BEING PROVIDED PRIMARILY BY A GENERALLY H-SHAPED APERTURE LOCATED CENTRALLY THEREOF AND CONFINED WELL WITHIN THE SIDE AND END MARGINS OF SAID REED, SAID H-SHAPED APERTURE HAVING THE PARALLELING SLOT PORTIONS THEREOF EXTENDING TRANSVERSELY OF SAID REED AND PARALLELING THE END MARGINS THEREOF, THE CONNECTING SLOT PORTION OF SAID HSHAPED APERTURE EXTENDING LONGITUDINALLY OF SAID REED ALONG THE MAJOR AXIS THEREOF, A PAIR OF INWARDLY AND OPPOSITELY DIRECTED JUXTAPOSED PANEL PORTIONS DEFINED BY SAID H-SHAPED APERTURE INWARDLY OF SAID SIDE MARGINS BETWEEN SAID PARALLELING SLOT PORTIONS, A CIRCULAR APERTURE CONFINED WITHIN EACH OF SAID PANEL PORTIONS AND IN TRANSVERSE ALIGNMENT ON OPPOSITE SIDES OF THE CONNECTING SLOT PORTION OF SAID H-SHAPED APERTURE BETWEEN THE PARALLELING SLOT PORTIONS THEREOF, SAID CIRCULAR APERTURES BEING DIMENSIONED TO DEFINE ELECTRICAL CONDUCTING NECK-LIKE AREAS BETWEEN THE CIRCULAR APERTURES AND THE SIDE MARGINS OF SAID REED AND ADJACENT PORTIONS OF SAID H-SHAPED APERTURE, THE NECK-LIKE AREAS BETWEEN SAID CIRCULAR APERTURES AND THE SIDE MARGINS OF SAID REED BEING STRETCHED OUT OF THE PLANE OF SAID REED TO TENSION SAID CENTRAL SNAP ACTION PORTION AND PROVIDE SAID REED WITH A DISHED SHAPE. 